1. Field of the Invention
The invention relates to an astable, magnetically coupled multivibrator including two power capacitors, which are connected in series to an input voltage and which can be alternatingly shorted via two switching transistors and via a transformer winding.
2. Brief Description of the Background of the Invention Including Prior Art
A Series 6500 A of eight feed power supply models is known from R. Myers and R. D. Peck, 200 kHz Power FET Technology in New Modular Power Supplies, HEWLETT-PACKARD Journal (August 1981), pages 3 to 7 and 10. These models provide a power of 50 watt direct current at 5, 12, 15, and 18 volt output voltage. The electrical construction of these components corresponds to switch-controlled power converters, which contain a multivibrator in a feedback circuit and where the frequency of the multivibrator is controlled. The multivibrator exhibits two MOSFET transistors which are switched precisely counter-cyclically, as well as two solid capacitors, a transformer, and a base resistor.
The frequency is controlled via the variable inductivity L of an electrically controllable inductor. This is a control coil with two E-shaped cores, which are operated according to the method of the saturation control. In this case, the control winding is disposed on the center web and the induction winding is provided as two individual windings connected in series and placed on the two outer webs of the cores. The core material has the property of a very high permeability and the magnetic flux densities in the two outer webs are maintained always in balance because of the low control current. (W. Seipel, Magnetic Components for High-Frequency Switching Power Supplies, HEWLETT-PACKARD Journal (August 1981), pages 8 and 9.)
An effort has been undertaken in the construction of the recited inductor to minimize the most disadvantageous properties of control throttle coils with saturation control (or, respectively, current-limiting controls or, respectively, saturation angle controls) (as known for example from H. Krakowski, The Magnetic Control Technique and its Application in the Power Supply Plants of the Federal German Post Office, Der Fernmeldeingenieur, Volume 8, Issue 7 (July 15, 1954), pp. 1 ff). This has certainly succeeded in part. Nevertheless, this inductor has remained the critical element in the power supply apparatus of the Series 6500 A.